Pedal board grounding question

[yeeshkul]

Guys i have this question:
I building a pedal board which has a metal case and a power supply inside. We have 3-lug mains sockets here, where  2 lugs are the standard AC juice and the third one is a safety/ground lug that must be used in case of metal cases. Now where shall i connect the yellow/green safety lug not to have ground-loop problems later? Normally it shall be connected to the case, but there will be the circuit ground on the case as well ... ?

[GibsonGM]

Generally, your power supply will have its ground connected to the chassis right next to where it enters the unit on a sturdy, well-connected lug  <very important, this is your safety ground!   Use lock washers...>.   Each circuit you're using will then be grounded to the chassis on a lug very close to its location, to avoid ground loops/RF noise.  Keeping the lugs as far apart as you can helps to avoid noise.  In the case of using line power stepped down to run your effects, there's no difference between the line ground and circuit ground, just as with your guitar cable's ground actually being connected to earth ground thru the amp.  There ARE means of attaining true isolation of the grounds, but that's a little overkill IMHO.

This isn't 'star grounding', but rather a 'buss style ground',  a technique that amp builders have used successfully for dozens of years.  The other option is to run each circuit ground to 1 common point (star ground).  I find that creates too much of an 'antenna effect' sometimes if wires aren't placed just right. 

You should check out some tube amp building forums, such as 18Watt.com, for tips on grounding for best results.   Things like isolating the in/output jacks from the chassis and to a common ground point also help avoid noise, and a small amount of trial and error might be required, too! 

Be careful with that line voltage...I ALWAYS check for AC and DC in places where it shouldn't be when working with line voltage before touching a project on first power up - you never know!!  How about a wall wart power supply? No trafo to build into your unit... 

[yeeshkul]

Mike thank you very much for your answer, i was thinking about the ground-loop enclosed this way:

pedal board signal jack -> cable -> amp chassis -> amp AC ground wire -> AC mains -> pedal board power supply AC ground wire -> chassis -> pedal board signal jack.

But this may be just to much ...

Keeping the lugs as far apart as you can helps to avoid noise.

I am not sure i understand what lugs you mean here

the rest is clear, i have my supply built already so i really want to use it. The "hot" part is isolated from chassis by 1mm thick plactic floor (there is also paint on the chassis) and there is also a cuprextit barrier(the metal side towards circuits) in between the supply and the circuits to prevent some sort of electromagnetic interaction.
thanks again, Jan